Multi-rate polyphase DSP and LMS calibration schemes for oversampled data conversion systems

—Architectural schemes for low-power calibration of oversampled analog-to-digital (A/D) systems are presented. Conventional full-rate least-mean squares (LMS) calibration has two well-known limitations: slow convergence and increased computational complexity/power dissipation for higher adaptive filter orders and sampling frequencies. Half(fs/2) and quarter-rate (fs/4) LMS calibration for oversampled A/D decimators are used to reduce the computational complexity. Noble identities and polyphase decimation are used to implement these schemes to match digital noise-cancellation filters (NCF) to the corresponding transfer functions of an analog fourth-order cascade sigma-delta ( ADC. Energy savings up to 30% compared to conventional full-rate (fs) schemes are confirmed using an Altera Stratix II fieldprogrammable gate array (FPGA). The analog front-end comprises a switched-capacitor 2-2 cascade ADC implemented in 0.13μm CMOS. Using differential-pair opamps with gains of only 22 db and a...

• Type: Journal
• Year: 2011
• Where: ICASSP
• Authors: Subhanshu Gupta, Yi Tang, Kuang-Wei Cheng, Jeyanandh Paramesh, David J. Allstot
• Keywords: Analog Fourth-order Cascade, Calibration, Full-rate Least-mean Squares, ICASSP 2011, Signal Processing